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OCR A-LEVEL Biology > Module 2 Section 2 - Biochemical Tests for Molecules > Flashcards

Module 2 Section 2 - Biochemical Tests for Molecules Flashcards

1
Q

What is the biochemical test for sugars

A

Benedict’s test

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2
Q

What 2 groups can sugars be classified as

A

Reducing or non reducing

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3
Q

The Benedict’s test differs….

A

Depending on the type of sugars you’re testing for

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4
Q

What do reducing sugars include

A

All monosaccharides and some disaccharides

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5
Q

What do you add to a sample of reducing sugars to test for it

A

Benedict’s reagent

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6
Q

What other step do you do to the sample after adding the Benedict’s reagent

A

Heat it in a water bath that has been brought to the boil

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7
Q

How does the colour of the precipitate change

A

Blue - Green - yellow - orange - brick red

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8
Q

What happens if the test is positive

A

A coloured precipitate will form

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9
Q

Why do I always add excess Benedict’s solution

A

To make sure all the sugar reacts

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10
Q

What can you conclude about the test

A

The higher the concentration of reducing sugars the further the colour change goes

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11
Q

What happens if the test of the reducing sugars is negative

A

There still could be non reducing sugars present

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12
Q

What is the first step of breaking down non reducing sugars

A

You have to break them down to monosaccharides

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13
Q

How do you break down the sugar to a monosaccharide to test for non reducing sugars

A

Get a new sample of the test solution, add dilute hydrochloric acid and carefully heating it in a water bath that has been brought to a boil

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14
Q

After diluting hydrochloric acid and heating it what do you do to the sample to test for non reducing sugars

A

You neutralise it with sodium hydrogencarbonate and then carry the test out as you would for reducing sugars

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15
Q

What happens if the test is positive

A

It will form a coloured precipitate

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16
Q

What happens if the test is negative

A

The solution will stay blue meaning it doesn’t contain any sugars

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17
Q

What is glucose best tested using

A

Test strips coated in reagent

18
Q

What happens if glucose is present

A

A colour change

19
Q

What can the colour change be compared to

A

A chart which gives the indication of concentration of glucose present

20
Q

What are the strips useful for

A

Testing a person’s urine for glucose - indicates they may have diabetes

21
Q

What test is used for starch

A

Iodine test

22
Q

What do you add to the test sample

A

Iodine which is dissolved in potassium iodide solution

23
Q

What happens if starch is present

A

The sample changes colour from brown/orange to a dark blue/black colour

24
Q

What happens if no starch is detected

A

It stays brown/orange colour

25
Q

What test is used for proteins

A

Biuret test

26
Q

What does the test solution for testing protein need to be

A

Alkaline

27
Q

How do you make the test solution alkaline

A

Add a few drops of sodium hydroxide solution

28
Q

After adding sodium hydroxide solution what do you add

A

Copper (II) sulfate solution

29
Q

What happens if protein is present

A

The solution turns purple

30
Q

What happens if there no protein present

A

The solution stays blue

31
Q

what test is used for lipids

A

the emulsion test

32
Q

what is the first stage of the emulsion test

A

shaking the test substance with ethanol for about a minute

33
Q

what do you do after shaking the test substance and ethanol

A

pour the solution into the water

34
Q

what happens if a lipid is present

A

the solution will turn milky

35
Q

what conclusion can be made about this test

A

the more lipid there is the more noticeable the milky colour will be

36
Q

what happens if the there are no lipids present

A

the solution will stay clear

37
Q

what is used to determine the concentration of a glucose solution

A

colourimeter

38
Q

how do you get a quantitative estimate for how much glucose is in a solutions

A

you can use benedicts reagent and a colourimeter

39
Q

what is a colourimeter

A

a device that measures the strength of a coloured solution by seeing how much light passes through t

40
Q

what does a colourimeter measure

A

absorbance

41
Q

the more the colour of the solution is……

A

the higher the absorbance is

42
Q

when is it easiest to measure the concentration of glucose

A

after the test is finished. meaning the higher the glucose concentration the lower absorbance of the solution

OCR A-LEVEL Biology (48 decks)

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